Apparatus for the digestion of nitrocellulose



. y 1933- M. G. MILLIKEN' I 1,911,201

APPARATUS FOR THE DIGESTION OF NITROCELLULOSE Filed May 29, 1929 I-'5'T-ZZ-TZ- 211 25515551 }152129 :fffY-E"111 iiiiii5:551:13

Patented May 30, 1933 P A T E IEAHLON G. MILLIKEN, 0F IPARLIN', NEWJERSEY, ASSIGNOR T0 HERCULES POWDER COMPANY, OF WILEIINGTON, DELAWARE, ACORPORATION OF DELAWARE APPARATUS FOR THE DIGESTION 0F NITBOGELLULOSEApplication filed May 29, 1929.

My invention relates to an improvement in method and apparatus for thetreatment of nitrocellulose, and more particularly relates to a methodand apparatus for the digestion of nitrocellulose to effect reduction ofits viscosity, increase its stability, and for its purification.

As is well known in the production of nitrocellulose, cellulose, as forexample cotton, is subjected to nitration, then washed to tree it fromacids, then subjected to a boiling treatment or digestion and finallysubjected to further washing or other treatment for its purification. Inthe production of nitrocellulose heretofore the boiling treatment ordigestion of the nitrated cellulose has been carried out in large closeddigesters, containing, for example, 1000 cubic 'feet of water and i000pounds of nitrocellulose, the mass being heated to a temperature of from115 O.l32 C. for a period ranging from ten hours to thirty hoursdepending upon the nitrogen content of the nitrocellulose, by thecirculation through the nitrocellulose of heated water. Such procedurefor the digestion of nitrocellulose is disadvantageous for many reasons,chief among which are that it is impossible to quickly and uniformlyheat the large mass of nitrocellulose, the large mass is a source ofdanger, the nitrocellulose tends to pack and the removal of entrappedair and gas, which tends to keep portions of the mass out of contactwith the water, is difficult.

Further it has been found in the case of nitrocotton, that due topacking, when the nitrocotton loses its strength during the digestion,it is impractical to produce a nitrocotton with a viscosity much belowone-halt.

Now it is the object of my invention to provide a novel method andapparatus for the digestion 01 nitrocellulose whereby the disadvantagesof the prior procedure will be eliminated and whereby a nitrocelluloseof reduced viscosity and of greater stability and purity than heretoforewill be produced.

In accordance with my invention nitro Serial No. $66,921.

is forced under pressure together with a carrier liquid, as water,through a restricted passage, as a coil of relatively small crosssection, and provided with means adapted to control the discharge fromthe passage and effect a substantial equalization of the pressure in thecoil between the inlet and discharge ends, such as a standpipe,connected to the discharge end of the passage and adapted to aiiord ahead or back pressure, or restricted outlet provided by reducing thedischarge end of the passage or providing a valve thereon. The mixtureof carrier liquid and nitrocellulose pass through the passage togetherat a relatively high velocity and at a regulated temperature. On passingout of the passage the nitrocellulose may be subjected to such furthertreatment as is desired.

Further, my invention contemplates the provision of means for supplyingadditional carrier liquid to the mixture of nitrocellulose and carrierliquid at a. point adjacent the outlet from the coil, thus facilitatingdischarge of the nitrocellulose-carrier liquid mixture and avoidance or"jamming and at the same time assisting in washing out acid from thenitrocellulose and hence promoting its stability. 7

Having now indicated in a general way the nature and purpose of myinvention, 1 will proceed to a more detailed description thereof withreference to the accompanying drawing in which an apparatus inaccordance with my invention is shown diagrammatically, a form of valvefor controlling the outlet from the coil being shown in section. v

In the apparatus illustrated A indicates an agitating tub for thereception of nitrated cellulose to be digested and in which the nitratedcellulose is mixed with a car rier liquid, as water. B indicates a pumpadapted for drawing nitr ated cellulose and water from the tub A andforcing the mixture into and through the passage or coil C which isformed, for example, from a number of pipe sections connect-ed by returnbends. D indicates a tank for collecting the treated nitrocellulose. Aportion of the coil at the inlet end is jacketed as indicated at e, thejacket being provided with an inlet and out-let for steam adapted forheating the nitrocellulose and water, and a portion of the coil at itsoutlet end is jacketed as indicated at f, the jacket 7 being providedwith an inlet and outlet for water adapted for cooling the nitratedcellulose and water. The intermediate portion of the coil is preferablycovered with insulating material, for example asbestos, as indicated atg in order to maintain the desired temperature of the nitrocellulose andwater in the intermediate portion of the coil.

H indicates a valve comprising a casing adapted for connection to theoutlet end of the coil C and to a pipe 2' connected to a standpipe X.Within the casing is provided a valve seat on waich is adapted to seat aconical valve j, the valve being desirably arranged in line with theoutlet from the coil. The stem of valve extends externally of the casingthrough a stutling box Z and is provided at its outer end with a head onagainst which one end of a spring a abuts. The other end of spring aabuts against a stop 0 adjust-ably carried by a bracket 29 attached tothe casing. The valve j is thus yieldingly held on its seat by spring a,the tension of which is set to permit the valve to normally open againsta given pressure in the coil C and at the same time permit furtheropening or" the valve to free any jam of ni rocellulose which may occurat the valve dueto the packing tendency of the nitrated cellulose.

Adjacent the outlet end or the coil C just ahead of the valve H a pipe Eis let into the coil and connected to the discharge of a pump F, to theintake or which is connected a pipe G leading from a suitable supply ofwater, either an independent supply or that in or overflowed from tankD. The passage of water through pipe E is controlled by a valve 1.

The standpipe X, which forms a chamber, extends vertically a sufiicientdistance to provide a desirable head or back pressure and is providedwith a return bend and downward extension. X connected with the tank D.A vent pipe Y, controlled by a valve Z, is connected to the downwardextension X of the standpipe in order to avoid or control the creationof vacuum, and a pipe R, controlled by a valve S, is connected to thestandpipe and to a suitable source of air under pressure whereby thepressure created by the head in standpipe X may be relieved. Further, adirect connection between the end of coil C and tank D is made through apipe T controlled by a valve u, whereby direct discharge from the coil Cto tank D may be effected in cases of emergency.

\Vhile I have described the apparatus in accordance with my invention,as diagram matically illustrated, as including both a discharge controlvalve H and a standpipe X, it will be understood that the apparatus willbe effective with the use of a standpipe only for control of thedicharge from the coil through the back pressure from the head therein.

As a more specific example of a form of apparatus for use in connectionwith the digestion of, for example nitrocotton, the various elements arepreferably made of chrome steel, the coil may desirably have a diameterof three and one-half inches, and a length of say 2500-3000 feet whilethe standpipe X may be of a diameter of three and one-half inches andot' a height of 168 feet, affording a pressure of 72 pounds or such asto afi'ord a desirable head, depending upon the pressure desired in thecoil.

In the treatment of nitrocotton with the apparatus above described, andaccording to the method embodying my invention, and which forms thesubject matter of the copending application filed by me February 23,-1928, Serial No. 256,1i0, for example, nitrocotton, is placed in the tubA with Water in about the proportion of one nitrocotton to twenty-livewate the tub being desirably provided with an agita .ing device formixing the nitrocotton and W2 e mixture of nitrocotton and water is pumed through the coil at a pressure of about pounds per square inch, andat a substantial velocity, say, for example, about two feet per second,and the mixture of nitrocotton and water in the coil is brought to asuitable temperature, (say about 160 by the introduction or steam intothe jacket 0. A preferred range of temperature is from about C. orpossibly somewhat lower to about C, although a temperature as high as C.may be permissible. The valve j is set so as to permit the nitrocottonand water to discharge into the stand pipe X to be finally dischargedinto tank D and, as has been indicated, jamming of the nitrocotton isprevented by the fact that the valve is yieldingly held and on abuilding up of pressure, due to jamming of nitrocotton, will open widerand p rmit the passage of any jammed or matted nitrocotton. During thetreatment water unc er pressure is forced into the coil C adjacent tovalve H, through pipe E, and acts to insure operation of the valve H onjamming of the nitrated cotton and also to maintain the valve normallyat a desired open position. The water introduced into coil C throughpipe E also acts to increase the proportion of water to nitrated cottonat the point of discharge from the coil, thus facilitating the dischargeof the mixture and acting to wash out acidity from the nitrated cotton.The water admitted through pipe E may, as has been indicated, be drawnfrom an independent supply, or it may be drawn from tanlr D directly orindirectly, thus in efl ect recircu- 5 lating a part of the water fromthe nitrated cotton-water mixture discharged from the coil. The watermay be heated or at room temperature, and may be introducer into thecoil in quantity and under pressure varying with the characteristics oftie mixture and pressure within the coil and with the desired control ofvalve H.

After assing through valve H the nitrocotton and water will pass intostandpipe X in which it will ise to pass eventually to tank through thedo-.vnv.'ard extension X. The column of nitrocotton and water in thestandpipe X will aflord a head or back pressure on the valve H, whichwill be effective to control the action of the valve and 'he dischargefrom the coil.

In the operation of the apparatus described the discharge from coil Cwill, as has been indicated, be controlled by the valve H 535 an. thehead afforded in the standpipe X,

with the result that SUbStl-fiilitl equalization of pressures in thecoil C will be effected. lVhcre both the standpipe X and the valve H areused the head aflforded in the standpipe will act to balance valve iii,

to insure smooth and controlled action of the valve in its operation inrelievin any jam which may occur, and with valve H to control thedischarge from coil G. However, the apparatus, as will be clearlyunderstood, may be constructed without the valve l-l, control of thedischarge being obtained by use of the standpipe only, which in suchcase is connected directly to the discharge 40 end the coil C. Vi henthe valve H is omitted, it is only necessary to provide the standpipe Xof suflicient height, or alternatively, a suitable chamber, to provide ahead alfording sutlicient pressure for such control of the dischargefrom coil C as is nccessar to obtain a substantial equalizat 1 ofpressure in the coil, Further, it

i s clearly understood that the apparatus may be constructed without thestandpipe X, control of the discharge from coil C being affected by thevalve only, as fully described and claimed in the copending ap p icationfiled by me July 1%, 1928, Serial humber 299,808.

In connection with the apparatus embodving my invention, it will benoted that means, including the pipe ll, are provided for releasing thebaclr pressure from the head in standpipe X when desirable and,

69 including the pipe T, for discharging directly from the coil G intotank D when desired or in cases of emergency.

In connection with the apparatus herein described and embodying myinvention, it will be understood that various modifications and changesmay be made therein without departing from my invention.

It will be understood that the apparatus embodying my invention may beused for the treatment of cellulose other than nitrocellulose, as forexample, in connection with the purification treatment of cellulose,such as cotton, straw, comminuted wood, or the like.

This application constitutes a continuation in part of application forpatent for improvement in apparatus for the digestion of nitrocellulose,filed by me July 14, 1928, Serial No. 292,808.

What I claim and desire to protect by Letters Patent is:

1. Apparatus for the treatment of fluent material comprising a solidsuspended in a carrier liquid, including in combination an extendedconduit, means for forcing fluent material through said conduit, meansfor cooling fluent materials adjacent the discharge end of said conduitand means for creating a hydrostatic head exerting pressure on fluentmaterial within said conduit in opposition to said forcing means.

2. Apparatus for the treatment of fluent material comprising a solidsuspended in a carrier liquid, including in combination an extendedconduit, means for forcing fluent material through said conduit, meansfor heating fluent material within said conduit, means for coolingfluent material adjacent the discharge end of said conduit, and meansfor creating a hydrostatic head exerting pressure on fluent materialwithin said conduit in opposition to said forcing means.

Apparatus for the treatment of fluent material comprising a solidsuspended in a carrier liquid, including in combination an extendedconduit, means for forcing fluent material through said conduit, meansadjacent the inlet end of said conduit, for heating fluent materialwithin said conduit, means adjacent the discharge end of said conduitfor cooling fluent material within said conduit, means for maintainingthe temperature of fluent material within said conduit between theheating and cooling means, and means for creating a hydrostatic headexerting pressure on fluent material within said conduit in oppositionto said forcing means.

4. Apparatus for the treatment of fluent material comprisingnitrocellulose and a carrier liquid, including in combination a conduitof substantial length and of relatively small cross-sectional area,means for forcing fluent material through said conduit, means forheatingfluent material within said con duit adjacent the inlet endthereof, means for cooling fluent material within said conduit adjacentthe discharge end thereof, and a standpipe connected to the dischargeend of said conduit and adapted to receive fluent material dischargedfrom said conduit and to contain a column thereof exerting hydrostaticpressure in opposition to said forcing means.

5. Apparatus for the treatment of fluent material comprisingnitrocellulose and a carrier liquid, including in combination a conduithaving sections extending horizontally and sections extending upwardly,means for forcing fluent material through the conduit from its inlet endand means for exerting a hydrostatic head on fluent material Within theconduit in opposition to said forcing means.

6. Apparatus for the treatment of fluent material comprisingnitrocellulose and a carrier liquid, including in combination, a conduithaving sections extending horizontally and sections extending upwardly,means for forcing fluent material through the conduit from its inletend, a standpipe adapted to receive fluent material discl'iarged fromsaid conduit and to contain a column thereof exerting hydrostaticpressure in opposition to said forcing means.

7. Apparatus for the treatment oii' fluent material comprisingnitrocellulose and a carrier liquid including in combination, a conduitof substantial length and of relatively small cross sectional areacomprising a plurality of horizontally extending sections connectedtogether by return bends, the inlet end of the said conduit beinglocated at a level below its discharge end, means for forcing fluentmaterial through the conduit from its inlet end and a standpipe adaptedto receive fluent material discharged from said conduit and to contain acolumn thereof exerting hydrostatic pressure in opposition to saidforcing means.

In testimony of which invention, I have hereunto set my hand, at Parlin,New Jersey, on this 24th day of May, 19:29.

MAHLON G. MILLIKEN.

GERTEFEGATE or CORRECTION.

Patent No. 1,911,201. May 30, 1933.

MAHLON o. MILLIKEN.

It ishereby certified that error appears in. the printed specificationof the above numbered patent requiring correction as follows: Page 1,line 40, after "one-half" insert the worri "second"; and that the saidLetters Patent should be read with this correction therein that the samemay conform to the record of thecase in the Patent Office.

Signed and sealed this 22nd day of August, A. D. 1933.

Me J. Moore, (Seal) Acting Commissioner of Patents.

